ACTH and polymorphisms at steroidogenic loci as determinants of aldosterone secretion and blood pressure

The majority of genes contributing to the heritable component of blood pressure remain unidentified, but there is substantial evidence to suggest that common polymorphisms at loci involved in the biosynthesis of the corticosteroids aldosterone and cortisol are important. This view is supported by data from genome-wide association studies that consistently link the CYP17A1 locus to blood pressure. In this review article, we describe common polymorphisms at three steroidogenic loci (CYP11B2, CYP11B1 and CYP17A1) that alter gene transcription efficiency and levels of key steroids, including aldosterone. However, the mechanism by which this occurs remains unclear. While the renin angiotensin system is rightly regarded as the major driver of aldosterone secretion, there is increasing evidence that the contribution of corticotropin (ACTH) is also significant. In light of this, we propose that the differential response of variant CYP11B2, CYP11B1 and CYP17A1 genes to ACTH is an important determinant of blood pressure, tending to predispose individuals with an unfavourable genotype to hypertension

MicroRNAs in Aldosterone Production and Action

The secretion of aldosterone by the adrenal cortex is a tightly regulated process. Loss of this control can result in severe hypertension and end-organ damage, so detailed understanding of the various mechanisms by which the body regulates aldosterone biosynthesis is key. The emergence of microRNAs (miRNAs) as negative regulators of numerous physiological processes has naturally led to their study in the context of aldosterone production. We summarise several studies that have demonstrated a significant role for microRNAs in aldosterone biosynthesis and action, thereby presenting a possible therapeutic role in the treatment of common forms of hypertension such as primary aldosteronism. Furthermore, the presence of microRNAs in the circulation offers the prospect of accessible and informative biomarkers that may simplify the currently protracted and technically difficult diagnosis of such conditions

Effects of ACTH, dexamethasone, and adrenalectomy on 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) gene expression in the rat central nervous system

Using a highly sensitive quantitative RT-PCR method for the measurement of CYP11B1 (11β-hydroxylase) and CYP11B2 (aldosterone synthase) mRNAs, we previously demonstrated that CYP11B2 expression in the central nervous system (CNS) is subject to regulation by dietary sodium. We have now quantified the expression of these genes in the CNS of male Wistar Kyoto (WKY) rats in response to systemic ACTH infusion, dexamethasone infusion, and to adrenalectomy. CYP11B1 and CYP11B2 mRNA levels were measured in total RNA isolated from the adrenal gland and discrete brain regions using real-time quantitative RT-PCR. ACTH infusion (40 ng/day for 7 days, N=8) significantly increased CYP11B1 mRNA in the adrenal gland, hypothalamus, and cerebral cortex compared with animals infused with vehicle only. ACTH infusion decreased adrenal CYP11B2 expression but increased expression in all of the CNS regions except the cortex. Dexamethasone (10 μg/day for 7 days, N=8) reduced adrenal CYP11B1 mRNA compared with control animals but had no significant effect on either gene's expression in the CNS. Adrenalectomy (N=6 per group) significantly increased CYP11B1 expression in the hippocampus and hypothalamus and raised CYP11B2 expression in the cerebellum relative to sham-operated animals. This study confirms the transcription of CYP11B1 and CYP11B2 throughout the CNS and demonstrates that gene transcription is subject to differential regulation by ACTH and circulating corticosteroid levels

Simple guide to starting a research group

Conducting cutting-edge research and scholarship becomes more complicated with each passing year; forming a collaborative research group offers a way to navigate this increasing complexity. Yet many individuals whose work might benefit from the formation of a collaborative team may feel overwhelmed by the prospect of attempting to build and maintain a research group. We propose this simple guide for starting and maintaining such an enterprise

Regulation of Corticosteroidogenic Genes by MicroRNAs

The loss of normal regulation of corticosteroid secretion is important in the development of cardiovascular disease. We previously showed that microRNAs regulate the terminal stages of corticosteroid biosynthesis. Here, we assess microRNA regulation across the whole corticosteroid pathway. Knockdown of microRNA using Dicer1 siRNA in H295R adrenocortical cells increased levels of CYP11A1, CYP21A1, and CYP17A1 mRNA and the secretion of cortisol, corticosterone, 11-deoxycorticosterone, 18-hydroxycorticosterone, and aldosterone. Bioinformatic analysis of genes involved in corticosteroid biosynthesis or metabolism identified many putative microRNA-binding sites, and some were selected for further study. Manipulation of individual microRNA levels demonstrated a direct effect of miR-125a-5p and miR-125b-5p on CYP11B2 and of miR-320a-3p levels on CYP11A1 and CYP17A1 mRNA. Finally, comparison of microRNA expression profiles from human aldosterone-producing adenoma and normal adrenal tissue showed levels of various microRNAs, including miR-125a-5p to be significantly different. This study demonstrates that corticosteroidogenesis is regulated at multiple points by several microRNAs and that certain of these microRNAs are differentially expressed in tumorous adrenal tissue, which may contribute to dysregulation of corticosteroid secretion. These findings provide new insights into the regulation of corticosteroid production and have implications for understanding the pathology of disease states where abnormal hormone secretion is a feature

Interaction between Metformin, Folate and Vitamin B 12 and the Potential Impact on Fetal Growth and Long-Term Metabolic Health in Diabetic Pregnancies

From MDPI via Jisc Publications RouterHistory: accepted 2021-05-25, pub-electronic 2021-05-28Publication status: PublishedFunder: Medical Research Council; Grant(s): MR/R023166/1, MR/T001828/1Funder: British Heart Foundation; Grant(s): FS/4yPhD/F/20/34130Metformin is the first-line treatment for many people with type 2 diabetes mellitus (T2DM) and gestational diabetes mellitus (GDM) to maintain glycaemic control. Recent evidence suggests metformin can cross the placenta during pregnancy, thereby exposing the fetus to high concentrations of metformin and potentially restricting placental and fetal growth. Offspring exposed to metformin during gestation are at increased risk of being born small for gestational age (SGA) and show signs of ‘catch up’ growth and obesity during childhood which increases their risk of future cardiometabolic diseases. The mechanisms by which metformin impacts on the fetal growth and long-term health of the offspring remain to be established. Metformin is associated with maternal vitamin B12 deficiency and antifolate like activity. Vitamin B12 and folate balance is vital for one carbon metabolism, which is essential for DNA methylation and purine/pyrimidine synthesis of nucleic acids. Folate:vitamin B12 imbalance induced by metformin may lead to genomic instability and aberrant gene expression, thus promoting fetal programming. Mitochondrial aerobic respiration may also be affected, thereby inhibiting placental and fetal growth, and suppressing mammalian target of rapamycin (mTOR) activity for cellular nutrient transport. Vitamin supplementation, before or during metformin treatment in pregnancy, could be a promising strategy to improve maternal vitamin B12 and folate levels and reduce the incidence of SGA births and childhood obesity. Heterogeneous diagnostic and screening criteria for GDM and the transient nature of nutrient biomarkers have led to inconsistencies in clinical study designs to investigate the effects of metformin on folate:vitamin B12 balance and child development. As rates of diabetes in pregnancy continue to escalate, more women are likely to be prescribed metformin; thus, it is of paramount importance to improve our understanding of metformin’s transgenerational effects to develop prophylactic strategies for the prevention of adverse fetal outcomes

The effect of slow-wave sleep and rapid eye-movement sleep interventions on glycaemic control: a systematic review and meta-analysis of randomised controlled trials

Poor glycaemic control is found in diabetes, one of the most common, serious, non- communicable diseases worldwide. Trials suggest a relationship between glycaemic control and measures of sleep including duration and quality of sleep. Currently, the relationship between specific sleep stages (including slow-wave sleep (SWS), a sleep stage mainly found early in the night and linked to restorative functioning) and glycaemic control remains unclear. This systematic review aimed to synthesise the evidence of the effectiveness of specific sleep stage manipulation on measures of glycaemic control (insulin resistance, fasting and post-prandial glucose and insulin). Public databases (e.g. psychINFO, MEDLINE, Academic Search Complete, psychARTICLES, OpenDissertations, Scopus and Cochrane library) were searched for randomised controlled trials. Trials were included if they involved direct manipulation of SWS and/or rapid eye-movement sleep to explore the impact on measures of glycaemic control (insulin resistance, fasting and post-prandial glucose and insulin). Eight trials met the eligibility criteria, with four providing data for inclusion in one of the three meta-analyses. Insulin resistance was significantly higher in the SWS disruption when compared to the normal sleep condition, (p = 0.02). No significant differences were found for measures of fasting or post-prandial glucose or insulin. Risk of bias was considered low for performance bias, detection bias and incomplete outcome data, with unclear selection bias. This is an emerging area of research and this review provides preliminary findings and recommendations for future research around optimising sleep stage disruption (to further explore mechanisms) and sleep stage enhancement techniques (to explore potential interventions)

MAGIC (Maternal Glucose in Pregnancy) - Understanding the glycemic profile of pregnancy, intensive CGM glucose profiling and its relationship to fetal growth. An observational study protocol

Background: Continuous glucose monitoring (CGM) provides the most objective method of assessing glucose in daily life. Although there have been small, short-term physiologic studies of glucose metabolism in ‘healthy’ pregnant women a comprehensive, longitudinal description of changes in glucose over the course of pregnancy and how glucose dysregulation earlier in pregnancy relates to traditional third trimester screening for gestational diabetes, fetal growth and pregnancy outcomes is lacking. This study aims to characterise longitudinal changes in glycemia across gestation using CGM, in order to understand the evolution of dysglycemia and its relationship to fetal growth. Method/design: A multi-centre, prospective, observational, cohort study of 500 healthy pregnant women, recruited in the first trimester of pregnancy. Masked CGM will be performed for a 14-day period on five occasions across pregnancy at ~ 10-12, 18-20, 26-28, 34-36 weeks gestation and postnatally. Routinely collected anthropometric and sociodemographic information will be recorded at each visit including: weight, height, blood pressure, current medication. Age, parity, ethnicity, smoking will be recorded. Blood samples will be taken at each visit for HbA1c and a sample stored. Details on fetal growth from ultrasound scans and the OGTT results will be recorded. Maternal and neonatal outcomes will be collected. CGM glucose profiling is the exposure of interest, and will be performed using standard summary statistics, functional data analysis and glucotyping. The primary maternal outcome is clinical diagnosis of GDM. The primary neonatal outcome is large for gestational age (LGA) (>90th centile defined by customised birthweight centile). The relationship of glucose to key secondary maternal and neonatal outcomes will be explored. Discussion: This study will ascertain the relationship of maternal dysglycemia to fetal growth and outcomes. It will explore whether CGM glucose profiling can detect GDM before the OGTT; or indeed whether CGM glucose profiling may be more useful than the OGTT at detecting LGA and other perinatal outcomes. Trial registration: ISRCTN 5706303 https://www.isrctn.com/ISRCTN15706303 Registration date: 13th March 2023

Investigations of Aerobic Methane Oxidation in Two Marine Seep Environments: Part 2—Isotopic Kinetics

During aerobic oxidation of methane (CH4) in seawater, a process which mitigates atmospheric emissions, the 12C‐isotopologue reacts with a slightly greater rate constant than the 13C‐isotopologue, leaving the residual CH4 isotopically fractionated. Prior studies have attempted to exploit this systematic isotopic fractionation from methane oxidation to quantify the extent that a CH4 pool has been oxidized in seawater. However, cultivation‐based studies have suggested that isotopic fractionation fundamentally changes as a microbial population blooms in response to an influx of reactive substrates. Using a systematic mesocosm incubation study with recently collected seawater, here we investigate the fundamental isotopic kinetics of aerobic CH4 oxidation during a microbial bloom. As detailed in a companion paper, seawater samples were collected from seep fields in Hudson Canyon, U.S. Atlantic Margin, and atop Woolsey Mound (also known as Sleeping Dragon) which is part of lease block MC118 in the northern Gulf of Mexico, and used in these investigations. The results from both Hudson Canyon and MC118 show that in these natural environments isotopic fraction for CH4 oxidation follows a first‐order kinetic process. The results also show that the isotopic fractionation factor remains constant during this methanotrophic bloom once rapid CH4 oxidation begins and that the magnitude of the fractionation factor appears correlated with the first‐order reaction rate constant. These findings greatly simplify the use of natural stable isotope changes in CH4 to assess the extent that CH4 is oxidized in seawater following seafloor release

Investigations of Aerobic Methane Oxidation in Two Marine Seep Environments: Part 1—Chemical Kinetics

Microbial aerobic oxidation is known to be a significant sink of marine methane (CH4), contributing to the relatively minor atmospheric release of this greenhouse gas over vast stretches of the ocean. However, the chemical kinetics of aerobic CH4 oxidation are not well established, making it difficult to predict and assess the extent that CH4 is oxidized in seawater following seafloor release. Here we investigate the kinetics of aerobic CH4 oxidation using mesocosm incubations of fresh seawater samples collected from seep fields in Hudson Canyon, U.S. Atlantic Margin and MC118, Gulf of Mexico to gain a fundamental chemical understanding of this CH4 sink. The goals of this investigation were to determine the response or lag time following CH4 release until more rapid oxidation begins, the reaction order, and the stoichiometry of reactants utilized (i.e., CH4, oxygen, nitrate, phosphate, trace metals) during CH4 oxidation. The results for both Hudson Canyon and MC118 environments show that CH4 oxidation rates sharply increased within less than one month following the CH4 inoculation of seawater. However, the exact temporal characteristics of this more rapid CH4 oxidation varied based on location, possibly dependent on the local circulation and biogeochemical conditions at the point of seawater collection. The data further suggest that methane oxidation behaves as a first‐order kinetic process and that the reaction rate constant remains constant once rapid CH4 oxidation begins